Hydraulic pump



Jan. 22, 1963 o. w. scHEFLow 3,074,345

HYDRAULIC PUMP t. a a L INVENTOR. oLlvER' w. scHEFL-ow BY M ATTORNEYJan. 22, 1963 o. w. scHr-:FLOW

HYDRAULIC PUMP 3 Sheets-Sheet 2 Filed July 27, 1959 INVENTOR. OLIVERSCHEFLOW A Tram/E( Jan. 22, 1963 o. w. SCHL-:FLOW 3,074,345

HYDRAULIC PUMP Filed July 27, 1959 3 Sheets-Sheet 3 INVENTOR. OLIVER W.SCHEFLOW wmf ATTORNEY United States @arent @ffice lfatenteel Jan, 22,lg3d 3,074,345 HYDRAULIC PUB/m @liver Waller Seheflow, Kalamazoo, Mich.,assigner, by mesne assignments, to Pneumolynamics Corporation,Cleveland, Ghia, a corporation of Delaware Filed July 27, 1959, Ser. No.829,864 7 Claims. (Si. 103-37) This invention relates generally tohydraulic pumps and more particularly to a new and improved hydraulicpump incorporating a valve mechanism which operates to change theeffective displacement.

It is an important object of this invention to provide a new andimproved valving mechanism for a wobble plate type pump.

It is another object of this invention to provide a valving mechanismfor wobble plate type pumps which can be adjusted or operated to changethe effect of displacement of the mechanism.

lt is another object of this invention to provide a wobble plate pumpwith a new and improved valve structure which can be operated to changethe effective displacement of the pump in response to predeterminedoperating conditions.

It is still another object of this invention to provide a wobble platepump in combination with a new and improved valve device which operatesto maintain a predetermined maximum output pressure in the pump.

It is still another object of this invention to provide a wobble platepump in combination with a vali/ing device which is operable while thepump is functioning to change the effective displacement of the pumpfrom zero to the maximum pump displacement.

Further obg'ects and advantages will appear from the followingdescription and drawings, wherein:

FIGURE l is a longitudinal section of a preferred wobble plate pumpincorporating this invention;

FIGURE 2 is an exploded perspective view of the valve control structure;

FGURE 3 is a cross section taken along 3 3 of FIG- URE l illustrating`the valving operation in a full ilow position;

FIGURES 4A through 4J are schematic illustrations of the progressivevalving operation under a full ow condition;

FIGURE 5 is a View similar to FIGURE 3 showing the valving structureoperated to a position wherein the effective displacement of the pump iszero; and

FIGURES 6A through 6I are schematic illustrations of the progressivevalving operation under a zero ilow condition when the etfectivedisplacement of the pump is zero.

In the past, variable displacement wobble plate type pumps have normallyachieved their variable displacement function by changing the angle ofthe wobble plate. However, the mechanisms for changing the angularposition of the wobble plate to change the displacement of the pumpproduces structural mounting and adjustment problems. In a wobble platepump incorporating this invention, the wobble plate is maintained in afixed angle regardless of the required displacement of the overalldevices so that the wobble plate can be securely and rigidly mounted.

The pump includes a housing or body lul) formed with an axiallyextending bore ill in which the pump mechanism is positioned. The outerend of the bore ll is closed by an end cap l2 through which a rotatabledrive shaft E3 projects. One end of a cylinder block ld is held againsta thrust member i6 by a spacer 17. One end of the spacer 17 engages aradial wall 18 on the cylinder` block 14 and the opposite end of thespacer 17 engages the outer race 19 of the ball bearings 2l. The outerrace 1Q is in turn held in position by the end cap 12. Connected by aspline 22 to the drive shaft i3 is a rotor shaft 23 to which is keyed awobble plate 24. The wobble plate 2liis provided with a bearing race 26along which the ball bearings 2l, move. A forward bearing 4.3 ispositioned between the rotor shaft 23 and the cylinder block 14 andco-operates with the `bearings 2l. to support the rotor shaft 23 forrotation about its axis.

A thrust bearing 27 is mounted on the forward face of the wobble plate2d so that it is inclined relative to the axis of rotation of the wobbleplate. An advanced slipper 23 is positioned against the thrust bearing27 and is formed with a groove 2@ adapted to receive a spherical end 3lon each of a plurality of pistons 32 which move in individual cylinderbores 44- in the cylinder block 14. A return slipper 33 is formed with abore 3d for each piston 32 and a socket 3o which engages the oppositeside of each spherical end and cooperates with the advance slipper 28 toclamp the spherical ends in position. The return slipper 33 is alsoformed with a central socket 57 which engages a spherical end 33 formedon a spring member 3%. The spring member 3f should be either a wavesprinty or Belleville spring. The spring member 39 is in turn positionedby engagement with the wall of a central bore il formed in the cylinderblock ital and the outer race i2 of the forward antifriction bearing 43.The engagement of the spherical end 38 with the central lsocket 37produces a force to hold the return slipper 33 in tight `engagement witheach of the spherical ends 3i on the pistons 32 and in turn maintainsthem in engagement with the advance slipper 28. This force also operatesto maintain the advance slipper 28 in Contact with the thrust bearingZ7.

The cylinder yblock ltdoes not rotate with the rotor shaft 23 sorotation of the rotor shaft, and in turn the wobble plate 242A, producesreciprocating motion of the pistons 32 relative to the cylinder blockla. The cylinder bores 2l/l are parallel and symmetrically arrangedaround the rotor shaft axis 23. The number of pistons 32 is determinedby the particular ydesign requirement of the pump. ln the illustratedembodiment, there are eight pistons and cylinder bores, so each of thepistons is displaced 45 in its cycle of operation from the adjacentpiston and relatively even llow characteristic is provided. lf a'smaller number of pistons are used, the cycle spacing between adjacentpistons will be greater.

Each of the cylinder bores la is open at a port or valving face loformed in the cylinder block ld. A valve ring i7 is positioned betweenthe valving face ad and the thrust member 16 and operates tosequentially provide communication between the cylinderbores and thehigh and low pressure zones which will be discussed below. The valvering i7 is iiournalled on the outer cylindrical surface 48 of aneccentric or cam member 49. As best shown in FIGURE 3, the eccentricmember i? is formed with an inner cylindrical surface 5l having an axis52 displaced from the axis 53 of the outer cylindrical face 48. A sleevebearing S4 is positioned within the inner cylindrical surface 5l and isin turn mounted on the forward end of the rotor shaft 23.

Referring again to FGURE l, the eccentric member 49 and the sleevebearing 54 are secured in position on the rotor shaft 23 by a nut 56. Apin 57 extends through a rst slot 5S in the rotor shaft 23 and thesleeve bearing 5d into an axial slot 59 in the eccentric member 49.Therefore, the eccentric member 49 rotates with the rotor shaft 23 andcauses the valve ring d'7 to move eccentrically around the axis 53 asthe rotor shaft 23 rotates. This causes radial movement of the valvering 47 relative to the cylinder bores 44 and produces the desiredvalving operation.

Liquid at low pressure is supplied to the pump through an inlet port 6Iin the housing 1i) and a radial port 62 in the spacer I7 so that theinner cavity of the pump is lled with liquid at low pressure. The spacerI7 is formed with a rib 63 which engages the housing 10 and in`co-operation therewith, forms a forward or high pressure chamber 64which is open through its high pressure or outlet port 66. The highpressure chamber communicates through the plurality of inclined ports 68with an annular cavity 67 ,defined in part by the outer surface of thevalve ring 47. Communication with an inner portion of the valving ring47 and `an inner cavity 69 is provided through a plurality of lowpressure passages 7l. The valve ring 47 is formed with an annular grooveproviding an inner face Til and a plurality of axial ports 72 so thatliquid at low pressure is provided on both sides of the valve platealong the inner portion thereof. Supply of low pressure liquid passesthrough the ports 6l and 62V to the inner cavity 69. From the innercavity 69, it passes through the low pressure passages 71 to the innerarea of the valve ring 47'.

In FIGURE l, both of the cylinder bores 44, which are shown in the planeof the section, are closed by the valve ring 47. However, reference toFIGURES 3 and 4 will illustrate how the valve ring operates. Thelowermost piston 32 is in the forward or dead center position asillustrated in FIGURE l and is closed by the valve ring 47.V

Also, the uppermost piston 32 is in the top dead center position yand isalso closed by the valve ring 47. However, the three pistons 32 andtheir cylinder bores 44, which are located to the right of thecenterline as viewed in FIGURE 3, are open to the low pressure zone. Atthe same time, the three cylinder hores 44 to the left of the centerlineare open to the high pressure zone in the annular cavity 67. If lthedirection of the rotation of the rotor shaft 23 is conntercloclrwise asviewed in FIGURE 3, liquid is drawn into each of the cylinder bores 44as the pistons 32 move from the bottom dead center position to the topdead center position. Then, as the pistons in the left side from thecenterline move forward pressurizing the liquid -in the cylinder bores,liquid is pumped out of the cylinder bores into the high pressure zonein the cavity 67 around the valve ring 47.

The operation of a piston through one complete cycle is illustrated inFIGURES 4A through 4]. In FIGURE 4A, the piston 32 is in the bottom deadcenter position and the valve ring 47 closes the cylinder bore 44. Asthe piston 32 starts to move back toward the top Vdead center position,the valve ring 47 operates to provide communication with the lowpressure zone withinthe valve ring so liquid is drawn into the cylinderbore 44 as indicatedv by the arrows. This condition continues throughFIG- URES 4B, 4C, and 4D. When the piston 32 reaches the top dead centerposition, the cylinder is filled with liquid and the valve ring 47 againcloses the cylinder bores 44 as shown in FIGURE 4E. On the forwardstroke illustrated in FIGURES 4F, 4G, and 4H, the valve ring 47 providescommunication between the cylinder bores 44 and the high pressure zonearound the valve ring so the liquid in 4the cylinder is pumped into thehigh pressure zone. Again, when the piston 32 is in the bottom deadcenter position of FIGURE 4I, the original condition, as shown in FIGURE4A, is again reached and the valve nng 47 closes the cylinder bores 44.

In order to vary the effective displacement of the pump, la pressureoperated mechanism illustrated in FIGURES 1 and 2 is utilized. Locatedin the outer end of the housing is a piston 73 the right end of which ismaintained at a pressure equal to the pressure in the high pressure orforward chamber 64 by a liuid connection through the passages 74 and 76.The piston 73 engages a plunger 77 through which the pin S7 projects.The plunger 77 is positioned within an axial bore 78 in the rotor shaft23 and is resiliently urged toward the piston 73 by a spring 79 alsopositioned in the bore 78. The slot 53 formed in the rotor shaft 23 isinclined relative to the rotor shaft as best illustrated in FIGURE 2 sothat axial movement of the plunger 77 and pin 57 relative to the rotorshaft 23 causes the plunger 77 and pin 57 to rotate relative to therotor shaft 23. Normally, the spring 79 maintains the pin 57 in thepositions of FIGURES 1 and 3 so that the eccentric member 49 ispositioned as shown in FIGURE 3, which is the full dow position. If thehigh pressure exceeds a predetermined value, the piston 73 operates toovercome the spring 79 and move the plunger 77 inward along the bore 78.This causes the pin 57 to ride along the slot 58 and rotate relative tothe rotor shaft 23. Because the slot 59 on the eccentric member 49extends axially, rotation of the pin S7 relative to the rotor shaft 23produces relative rotation between the eccentric member 49 and the rotorshaft 23. ThisV changes the orientation of the eccentric axis 53 of theeccentric member 49 relative to the central axis 52 and at a maximummovement of the plunger 77 toward the spring 79, moves the elements tothe position shown in FIGURE 5. The sleeve bearing 54 is formed with aslot 55 to permit axial movement of .the plunger 77. At this time, theuppermost piston is in communication with the high pressure zone and thelowermost piston is in communication with the low pressure zone eventhough the upper and lower pistons are in their dead center positions atthis point.

Reference to FIGURES 6A through 6J will illustrate the valving operationwhen the piston 73 has operated to change the orientation of theeccentric member 49 to the position of FIGURE 5. Here again, theoperation of the device is schematically illustrated to show one piston32 in progressive positions through one complete cycle. In FIGURE 6A,the piston 32 is in the bottom dead center position and the valve ring47 provides communication between the cylinder bores 44 and the lowpressure zone. Therefore, as the piston moves toward its top dead centerposition as shown in FIGURE 6B, liquid is drawn into the cylinder bores44 from the low pressure zone. However, when .the piston 32 is in amidposition of its stroke as shown in FIGURE 6C, the valve ring 47closes the cylinder bores 44. Further movement of the elements causesthem to reach the condition of FIGURE 6D at which time the piston 32 isstill moving toward the top dead center position. However, the cylinderbore is now open to the high pressure zone so liquid is drawn from thehigh pressure zone into the cylinder bore rather than from the lowpressure zone. Communication is maintained between the cylinder bore 44and the high pressure zone through, the top dead center position ofFIGURE 6E and until the piston 32 returns to a midposition on its inwardstroke shown in FIGURE 6G. Since the highl pressure zone is maintainedin communication with the cylinder bore 44 from `the positions ofFIGURES 6C through 6G, the liquid which is received from the highpressure zone is merely returned to the high pressure zone causing azero elective displacement relative to the high pressure zone. As lthepiston 32 continues to move toward its bottom dead center positionthrough the positions of FIGURE 6H, communication is again establishedbetween the cylinder bore 44 and the low pressure zone. Therefore, theliquid received during the initial inward stroke from the low pressurezone is returned to the low pressure zone. The piston 32 therefore hasan effective displacement of zero since the liquid received from the lowpressure zone is returned to the low pressure zone and the liquidreceived from the high pressure zone is returned to the high pressurezone.

Normally, the piston 73 will not move the plunger 77 through a suiicientdistance to cause the pump to reach the zero displacement condition.However, it does function to automatically change the eifectivedisplacement of the pump to regulate or maintain a predeterminedpressure in the high pressure zone. I This predetermined pressure isdetermined by thev area of the piston 73 in relationship to the force ofthe spring 79. Because the J piston 73 operates to rotate the eccentricmember 49 gradually from the full ilow condition of FIGURE 3 toward thezero ow condition of FlGURE 5, an infinitely variable effectivedisplacement can be achieved so that the output pressure of the pump canbe maintained at the desired level. A pressure sensitive valve may beused in the passage 76 to port pressure to the piston 73 to decreasepressure differential between full flow and zero ow. Also, a owsensitive valve could be used at this point to maintain constant flowregardless of speed or pressure. ther sensing devices may be used asrequired to change tlovv.

lt should be understood that the above sequence discussed in connectionwith one piston 32 is repeated by each of the pistons as the pumpfunctions. VBecause the valve is operated automatically to change theeffective displacement of the pump through an infinite number ofconditions between the full flow or full displacement condition and thezero displacement condition, complete control is provided even thoughthe wobble plate 24 is xed in its angular position.

Although a preferred embodiment of this invention is illustrated, itwill be realized that various modifications of the structural detailsmay be made without departing from the mode of operation and the essenceof the invention. Therefore, except insofar as they are claimed in theappended claims, structural details may be varied widely withoutmodifying the mode of operation. Accordingly, the appended claims andnot the aforesaid detailed description are determinative of the scopeor" the invention.

l claim:

1. A hydraulic mechanism comprising a body, a rotary shaft rotatablymounted in said body, a plurality of cylinders having their longitudinalaxes arranged in parallel relation, a piston reciprocable in eachcylinder, means mounted on the shaft and engaging the pistons producingreciprocation of said pistons upon rotation of said shaft, a port opento each cylinder symmetrically positioned at equal distance from theaxis of said shaft, a member concentrically mounted on said shaft forrotation therewith having a bearing surface eccentric relative to saidshaft, an annular valve journalled on said bearing surface and abuttingadjacent ends of the cylinders, separate high and low pressure zonesleading to said valve with one portion of the valve forming a boundingsurface of the high pressure zone and another portion of the valveforming a bounding surface of the low pressure Zone, said valve byvirtue of rotation of said member progressively connecting saidcylinders to said low and high pressure zones, and means engaging saidmember and shaft responsive to pressure variations Within said high zoneto change the eccentric orientation of said member and valve relative tosaid shaft.

2. A hydraulic mechanism comprising a body, rotary shaft rotatablymounted in said body, a plurality of cylinders having their longitudinalaxes arranged in parallel relation, a piston reciprocable in eachcylinder, means mounted on the shaft and engaging the pistons producingreciprocation of said pistons upon rotation of said shaft, a port opento each cylinder symmetrically positioned at equal distance from theaxis of said shaft, a circular valve having a central axis and inner andouter faces mounted on said shaft with its central axis eccentricrelative to the axis of said shaft and abutting adjacent ends of thecylinders, a high pressure zone cornmunicating with one of said valvefaces, a low pressure zone communicating with the other of said valvefaces, the eccentric mounting of said valve causing said valve toprogressively connect said cylinders to said high and low pressure zonesupon rotation of said shaft, and pressure responsive means connected tosaid high pressure zone and said valve operable to change the eccentricorientation of said valve relative to said shaft at a predeterminedpressure in the high pressure zone.

3. A hydraulic mechanism comprising a body, a rotary shaft rotatablymounted in said body, a wobble plate member nonrotatably mounted on theshaft, a stationary cylinder block member disposed in the body andformed with a plurality of parallel cylinders, a piston reciprocable ineach cylinder, the wobble plate member engaging the pistons andproducing reciprocation of said pistons upon rotation of the wobbleplate member, a port open to each cylinder symmetrically positioned atequal distance from the axis of said shaft, a circular valve having acentral axis and inner and outer faces mounted with its central axiseccentric relative to the axis of said shaft and abutting adjacent endsof the cylinders, a high pressure zone communicating with the one ofsaid valve faces, a low pressure Zone communicating with the other ofsaid valve faces, the eccentric mounting of said valve causing saidvalve to progressively connect said cylinders to said high and lowpressure zones upon rotation of said shaft, and pressure responsivemeans connected to the high pressure zone and to said valve operable tochange the eccentric orientation of said central axis of said valverelative to the axis of said shaft at a predetermined pressure in thehigh pressure zone.

4. A hydraulic mechanism comprising a body, a wobble plate rotatablymounted in said body, a plurality of parallel cylinders, a pistonreciprocable in each cylinder, the wobble plate engaging the pistonsproducing reciprocation of said pistons upon rotation of said wobbleplate, a port open to each cylinder symmetrically positioned at equaldistance from the axis of rotation of said wobble plate, a circularvalve having a central axis and inner and outer faces mounted with itscentral axis eccentric relative to the axis of rotation of said wobbleplate and abutting adjacent ends of the cylinders, a high pressure zonecommunicating with one of said valve faces, a low pressure zonecommunicating with the other of said valve faces, the eccentric mountingof said valve causing said valve to progressively connect said cylindersto said high and low pressure zones upon rotation of said wobble plate,and pressure responsive means connected to the high pressure zone and tosaid valve operable to change tne eccentric orientation of said centralaxis of said valve relative to the axis of rotation of said wobble plateat a predetermined pressure in the high pressure zone.

5. A hydraulic mechanism comprising a body, a shaft rotatably mountedin. said body, a plurality of parallel cylinders, a piston reciprocablein each cylinder, means connecting said shaft and pistons producingreciprocation of the pistons in the cylinders in response to rotation ofsaid shaft, a valve surface, a plurality of ports in said valve surfacesymmetrically positioned at equal distance from said axis, each of saidports providing communication with one of said cylinders, a memberconcentrically mounted on said shaft having a bearing surface eccentricrelative to said shaft, an annular valve journalled on said bearingsurface engaging said valve surface and abutting adjacent ends of thecylinders, separate high and low pressure zones leading to said valvewith one portion of the valve forming a bounding surface of the highpressure zone and another portion of the valve forming a bonn g surfaceof the low pressure zone, a connecting mechanism between said shaft andmember including means responsive to pressure variations in said highpressure zone operable to change the rotational orientation of saidmember relative to said shaft at a predetermined pressure in the highpressure zone.

6. A hydraulic mechanism comprising a body, a shaft rotatably mounted insaid body, a plurality of parallel cylinders, a piston reciprocable ineach cylinder, means connecting said shaft and pistons producingreciprocation of the pistons in the cylinders in response to rotation ofsaid shaft, a valve surface, a plurality of ports in said valve surfacesymmetrically positioned at equal distance from said axis, each of saidports providing communication with one of said cylinders, a memberconcentrically mounted on said shaft having a bearing surface eccentricrelative to said shaft, an annular valve journalled on said bearingsurface engaging said valve surface and abutting adjacent ends of thecylinders, separate high and.

low pressure zones leading to said valve with one portion of the valveforming a boundingsurface of the high pressure zone and another portionof the valve forming a bounding surface of the low pressure zone, anoperator connected to the high pressure zone axially movable rela tiveto said shaft at a predetermined pressure in the high pressure zone, andconnecting means between said shaft and member connected to the operatorand operable to change the rotational orientation of said memberrelative t0 said shaft in response to axial movement of said.

operator.

7. A hydraulic mechanism comprising a body, a shaft rotatably mounted insaid body, arplurality of parallel.

cylinders, a piston reciprocable in each cylinder, means connecting saidshaft and pistons producing reciprocation of the pistons in thecylinders in response to rotation of said shaft, a valve surface, aplurality of ports in said valve surface symmetrically positioned atequal distance.

from said axis, each of said ports providing communication with one ofsaid cylinders, a member concentrically mounted on said shaft having abearing surface eccentric relative to said shaft, an annular valvejournalled on said bearing surface engaging said valve surface andabuttingV adjacent ends or" the cylinders, separate high and lowpressure zones leading to said valve with one portion of the valveforming a bounding surface of the high pressure zone and another portionof the valve forming a bounding surface of the low pressure zone, saidvalve by virtue of rotation of said member progressively connecting thecylinders to the low and high pressure zones a bore in said shaft, aninclined groove through the wall of said shaft open to said bore, anaxial groove in said mem er, a. plunger axially movable in said bore andconnected to the high pressure zone and provided with a projectionextending through said inclined groove into said axial `grooveconnecting said member for rotation with said shaft and the plungermovingvaxially in the bore at a predetermined pressure in the highpressure zone causing the projection to move along the inclined groovein the shaft and compelling the axial groove in the member to follow theprojection to provide rotation of the member relative to the shaft.

References Cited in the tile of this patent v- UNITED STATES PATENTS2,280,875

" (Addition to No. 1,146,899)

1. A HYDRAULIC MECHANISM COMPRISING A BODY, A ROTARY SHAFT ROTATABLYMOUNTED IN SAID BODY, A PLURALITY OF CYLINDERS HAVING THEIR LONGITUDINALAXES ARRANGED IN PARALLEL RELATION, A PISTON RECIPROCABLE IN EACHCYLINDER, MEANS MOUNTED ON THE SHAFT AND ENGAGING THE PISTONS PRODUCINGRECIPROCATION OF SAID PISTONS UPON ROTATION OF SAID SHAFT, A PORT OPENTO EACH CYLINDER SYMMETRICALLY POSITIONED AT EQUAL DISTANCE FROM THEAXIS OF SAID SHAFT, A MEMBER CONCENTRICALLY MOUNTED ON SAID SHAFT FORROTATION THEREWITH HAVING A BEARING SURFACE ECCENTRIC RELATIVE TO SAIDSHAFT, AN ANNULAR VALVE JOURNALLED ON SAID BEARING SURFACE AND ABUTTINGADJACENT ENDS OF THE CYLINDERS, SEPARATE HIGH AND LOW PRESSURE ZONESLEADING TO SAID VALVE WITH ONE PORTION OF THE VALVE FORMING A BOUNDINGSURFACE OF THE HIGH PRESSURE ZONE AND ANOTHER PORTION OF THE VALVEFORMING A BOUNDING SURFACE OF THE LOW PRESSURE ZONE, SAID VALVE BYVIRTUE OF ROTATION OF SAID MEMBER PROGRESSIVELY CONNECTING SAIDCYLINDERS TO SAID LOW AND HIGH PRESSURE ZONES, AND MEANS ENGAGING SAIDMEMBER AND SHAFT RESPONSIVE TO PRESSURE VARIATIONS WITHIN SAID